This invention relates to radar signal processing and in particular to an apparatus and method for estimating the velocity of a target from differences in a Doppler frequency shift between radar pulse returns of multi-pulse waveforms.
A pulsed radar system that extracts Doppler frequency shift of return radar pulses for the purpose of detecting moving targets and determining their radial velocity is referred to as a pulse Doppler radar. A pulse Doppler radar transmits, repetitively, modulated pulses for a certain time duration, which is referred to as the dwell time of the radar. The time period between each pulse or modulation is the interpulse period, and determines the pulse repetition frequency (PRF). It is common practice for the interpulse periods to be varied, thereby providing several pulse repetition frequencies or PRF's. Such radar systems typically have a relative high PRF in order to prevent ambiguities in the Doppler frequency shift.
A radar system and particularly a surveillance or search radar is used to detect aircraft targets and to determine ranges and bearing of such aircraft. The radar characteristics such as power, pulse width and pulse repetition frequency vary depending on the expected location of a target to be detected. However, certain detected targets that appear on a radar display are of more concern than others. For instance, in military applications it is important to not only detect a target, but also to determine the amount of threat a particular target represents. A good indication of the amount of threat is the measurement of the radial velocity of the target in order to determine if the target is rapidly heading in your direction is desirable to minimize the amount of electronic hardware required to determine such a velocity.